Method and apparatus for assigning colours to an image

ABSTRACT

A method and system for assigning colours to an image or part thereof, the method comprising: selecting a sequence of colours for assignment to the image or part thereof; determining a minimum intensity I MIN  within the image or part thereof; 
     determining a maximum intensity I MAX  within the image or part thereof; and determining relative intensity values RIV(i) for each pixel or voxel i according to; (I) where I(i) is an intensity of pixel or voxel I, and f is a preselected function (such as to re-arrange the normalized values); and assigning colours to at least some pixels in the image or part thereof based on the relative intensity values and an order of each of the colours in the sequence.

FIELD OF THE INVENTION

This application is a Continuation of U.S. patent application Ser. No.15/021,752, filed 14 Mar. 2016, which is a National Stage Application ofPCT/AU2014/000886, filed 10 Sep. 2014, which claims benefit of SerialNo. 2013903530, filed 13 Sep. 2013 in Australia and which applicationsare incorporated herein by reference. To the extent appropriate, a claimof priority is made to each of the above disclosed applications.

BACKGROUND OF THE INVENTION

A user may wish to alter an image for many reasons. For example, theimage may not have sufficient clarity and certain details may not beclearly visible, such as owing to dullness or a poor choice of colours.Moreover, image contrast, which generally relates to an entire image,may be unsatisfactory for allowing clear visualization of the details inone or more regions of the image. Zooming in a specific region cancurrently be done, but this does not allow visualization of localquantitative differences between pixels.

Alternatively, an image may be perceived as unattractive or unappealing.This is often due to the user's dislike of the colours of one or moreparts of the image, or of one or more object within the image. If theuser does not like the colours, or when the colours do not clearly showdetails the user wishes to see, changing the colours of parts or all ofthe image can be difficult or time-consuming.

SUMMARY OF THE INVENTION

According to a first broad aspect of the invention, there is provided amethod of assigning colours to an image or part thereof, comprising:

-   -   selecting a sequence of colours (that is, with a specific order)        for assignment to the image or part thereof (whether        automatically or manually);        -   determining a minimum intensity I_(MIN) within the image or            part thereof (such as the intensity value of the pixels or            voxels in the image or part thereof);        -   determining a maximum intensity I_(MAX) within the image or            part thereof (such as the intensity value of the pixels or            voxels in the image or part thereof); and        -   determining relative intensity values RIV(i) for each pixel            or voxel i according to:

${{RIV}(i)} = {f\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right)}$

where I(i) is an intensity of pixel or voxel i, and f is a preselectedfunction (such as to re-arrange the normalized values); and

-   -   assigning colours to at least some pixels in the image or part        thereof based on the relative intensity values and an order of        each of the colours in the sequence.

The method may include segmenting one or more colours within the imageor part thereof based on a non-threshold analysis of a colour profilecurve derived from the image or part thereof.

The process of assigning colours to an image, or one or more parts ofthe image, is referred to as quantitative colouring (QC). While QC canbe used to highlight features within an image, it can also be used to dothe reverse—that is, to obscure or mask details in parts of any image,or in the image. Furthermore, it can be used to change the colours afterthese colours have being segmented (i.e. grouped).

The present invention is intended to be used in all areas when imagesare used, but in particular for medical images (which are by default ina greyscale), or any other area where clear visualization of detail byscientists or radiologists is critical.

In one embodiment, the method comprises selecting colours or shades inthe original image and applying the method only to pixels or voxels ofthe colours or shades thus selected.

In one embodiment,

${f\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right)} = {\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right).}$

Thus, as a result of this method, a set of RIV values is created thatconstitute a coloured version of the original image or part thereof.

The method may include selecting automatically the image or a partthereof based on one or more criteria.

The method may include generating a new image by colouring the originalimage according to the sequence of colours.

According to a second broad aspect of the invention, there is provided acomputer program product comprising instructions that, when executed ona computing device, controls the device to perform the method describedabove. The computer program product may be stored on a computer-readablemedium, in some cases in permanent form, or transmitted.

According to a third broad aspect of the invention, there is provided animage produced by the method described above.

According to a fourth broad aspect of the invention, there is provided asystem for assigning colours to an image or part thereof, comprising:

-   -   a colour selector for selecting a sequence of colours for        assignment to the image or part thereof (whether automatically        or manually);    -   an intensity determiner for determining a minimum intensity        I_(MIN) within the image or part thereof (such as the intensity        value of the pixels or voxels in the image or part thereof), and        for determining a maximum intensity I_(MAX) within the image or        part thereof (such as the intensity value of the pixels or        voxels in the image or part thereof);    -   a relative intensity value determiner for determining a relative        intensity value RIV(i) for each pixel or voxel i according to:

${{RIV}(i)} = {f\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right)}$

where I(i) is an intensity of pixel or voxel i, and f is a preselectedfunction (such as to re-arrange the normalized values; and

-   -   a colour assignor for assigning colours to at least some pixels        in the image or part thereof based on the relative intensity        values and an order of each of the colours in the sequence.

In one embodiment, the system comprises a colour segmenter forsegmenting one or more colours within the image or part thereof based ona non-threshold analysis of a colour profile curve derived from theimage or part thereof.

The system may include selecting automatically the image or a partthereof based on one or more criteria.

The system may include an image outputter for generating a new image bycolouring the original image according to the assigned colours.

According to a fifth broad aspect of the invention, there is provided amethod for segmenting cluster of colours with similar visual appearance,comprising:

-   -   selecting one or more colours within a cluster of pixels or        colours to be segmented (whether automatically or manually);    -   determining colour vector directions originating from an        initially selected colour of said one or more colours;    -   creating a colour profile curve in plural directions starting        from an initially selected colour of said one or more colours        based on a minimum perceptible colour difference (relating to a        predefined notion of visual acuity); and    -   analysing the colour profile curve to determine which colours in        the cluster of colours have a substantially identical appearance        as the initially selected colour (such as by identifying points        in the colour profile curve corresponding to a—for        example—minimum or maximum distance between suitably selected        points and the curve).

According to this aspect of the invention, there is also provided asystem for segmenting cluster of colours with similar visual appearance,comprising:

-   -   a colour selector for selecting one or more colours within a        cluster of pixels or colours to be segmented (whether        automatically or manually);    -   a vector generator for determining colour vector directions        originating from an initially selected colour of said one or        more colours;    -   a profiler for creating a colour profile curve in plural        directions starting from an initially selected colour of said        one or more colours based on a minimum perceptible colour        difference (relating to a predefined notion of visual acuity);        and    -   an analyser for analysing the colour profile curve to determine        which colours in the cluster of colours have a substantially        identical appearance as the initially selected colour (such as        by identifying points in the colour profile curve corresponding        to a—for example—minimum or maximum distance between suitably        selected points and the curve).

The system may include an output for outputting the colour or colourshaving the substantially identical appearance as the initially selectedcolour.

It should be noted that any of the various individual features of eachof the above aspects of the invention, and any of the various individualfeatures of the embodiments described herein including in the claims,can be combined as suitable and desired.

BRIEF DESCRIPTION OF THE DRAWING

In order that the invention may be more clearly ascertained, embodimentswill now be described, by way of example, with reference to theaccompanying drawing, in which:

FIG. 1 is a schematic view of a quantitative colouring system accordingto an embodiment of the present invention;

FIG. 2 is a schematic view of the user interface and controller of thequantitative colouring system of FIG. 1;

FIG. 3 is a flow diagram of the operation of the quantitative colouringsystem of FIG. 1;

FIG. 4 illustrates the operation of the region of interest (ROI)selector of the quantitative colouring system of FIG. 1;

FIG. 5 is a flow diagram illustrating automated segmentation and displayof a cluster of colours with substantially the same visual appearance asinitially selected colours within an image, as performed by the coloursegmenter of the quantitative colouring system of FIG. 1;

FIG. 6 illustrates a colour as selected by the colour segmenter of thequantitative colouring system of FIG. 1 represented as a voxel in space;

FIG. 7 illustrates the creation of the vector of colours and the colourprofile curve by the quantitative colouring system of FIG. 1;

FIG. 8 illustrates the analysis of the colour profile within the vectorof colours of FIG. 7;

FIG. 9 illustrates the selection of the cluster of colours of similarvisual appearance as the selected colour by the quantitative colouringsystem of FIG. 1;

FIG. 10 illustrates additional analysis of the colour profile toincrease the size of cluster of colour of similar visual appearance asthe selected colour, and therefore the colour spectrum by thequantitative colouring system of FIG. 1;

FIG. 11 illustrates the operation of the relative intensity value (RIV)determiner of the quantitative colouring system of FIG. 1;

FIG. 12 illustrates the operation of the colour assignor of thequantitative colouring system of FIG. 1; and

FIG. 13 illustrates an example of the effect of the variation of the RIVon the relative importance of the selected colours of the image on thedisplayed image by the quantitative colouring system of FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS

According to an embodiment of the present invention, there is provided aquantitative colouring system, shown schematically at 10 in FIG. 1together with an image source 12 of an original image and an output ofsystem 10 in the form of a quantitatively coloured (QC) image 14.Broadly speaking, system 10 receives an original image from image source12, determines and assigns an ordered set of selected colours to theoriginal image, or to one or more parts thereof, and outputs outputimage 14 accordingly, with a different colour scheme from that of theoriginal image.

Image source 12 may comprise, for example, an image acquisition device,an image creation device or an image storage device, such as a camera, ascanner, a mobile telephone, or a computer. The original image maycomprise a picture, a map, or text, and may be provided to system 10 inany digital format. System 10 may also include image source 12, andthereby also produce the original image for quantitative colouring.

System 10 comprises a computing system, which typically is in the formof a computer but may be in the form of—for example—a mobile telephoneor tablet computer provided with suitable hardware and software. System10 includes a user interface comprising a display 16 a and a keyboard 16b, an output (not shown) in the form of a bus, and a controller (notshown). QC image 14 may be output in any suitable manner, such as bydisplaying to display 16 a, printing or transmission (via the bus), orstorage to a memory (whether of system 10 or otherwise).

FIG. 2 is schematic view of user interface 16 a,b and the controller 18of system 10. Controller 18 includes a processor 20 and a memory 22.Processor 20 includes a display controller 24 for controlling display 16a, an image reader and displayer 26, a region of interest (ROI) selector28, a colour selector 30, an automatic colour segmenter 32 (whichincludes a profiler 33 a and an analyser 33 b), a segmented colourdisplayer 34, a segmented colour modifier 36, a relative intensity value(RIV) determiner 38 (which includes an intensity determiner 39), acolour assignor 40 and a QC image outputter 42. The functions of each ofthese components are described below.

FIG. 3 is a flow diagram 50 of the operation of system 10 of FIG. 1.Each step corresponds to the operation of, respectively, image readerand displayer 26, region of interest (ROI) selector 28, colour selector30, automatic colour segmenter 32, segmented colour displayer 34,segmented colour modifier 36, relative intensity value (RIV) determiner38, colour assignor 40 and QC image outputter 42. Thus, at step 52, theoriginal image is read/inputted and displayed to display 16 a. At step54, the user uses user interface 16 b to select one or more regions ofinterest (ROIs) for quantitative colouring. The default setting is toquantitatively colour the whole image and, in automatic operation system10—rather than the user—selects the parts of the image to bequantitatively coloured based on predefined criteria. The operation ofregion of interest (ROI) selector 28 is further illustrated at 70 inFIG. 4.

Optionally, step 54 may be done by image segmentation using asegmentation algorithm to segment a specific object, or any other meansfor automatically identifying (or segmenting) parts of an image.

At step 56, colour selector 30 selects (whether under user or automatedcontrol) the colour(s) to be assigned to the image. This selection maybe made from some or all of the colours in the original image or in theselected ROI(s). If under manual control, colour selector 30 controlssystem 10 to display a panel from which the user can select thecolour(s) that he or she wishes the ultimate QC image 14 to have. Ifunder automated control, colour selector 30 generates the requiredselection based on one or more predefined criteria; for example, colourselector 30 may select a user-specified or predefined number of equallyspaced colours from the existing colour palette of the original image.

The order in which the colours are selected also indicates the order inwhich they should be subsequently assigned, from first to last. Hence,the ordered set of selected colours constitutes a sequence of colours.Colour selector 30 is also user controllable to subsequently modify theselection of colours or their order in the sequence, by displaying thesequence of colours on display 16 a for user manipulation.

When this colour or these colours have been selected, colour segmenter32 then, at step 58, automatically segments (or categorizes) colourswithin the original image. This process of colour segmentation isillustrated schematically in FIGS. 5 to 10 and, in broad terms, involvessegmenting the ROI(s) into plural individual segments based on colour.This is performed because the original image may not contain a simplepalette of colours the readily defines clear delineated regions. Theremay be a smooth colour gradient from one (e.g. red) pixel to another(e.g. blue) pixel; segmentation determines where a suitable boundarybetween these pixels should lie, such that two (in this example) regionsor image segments may be defined. It should be noted that segmentationmay not always be required or desired, in which processing will passfrom step 56 to step 64 (see below). In addition, segmentation may beperformed at other points in the processing such as before step 56, inwhich case steps 58 to 62 (discussed below) would precede step 56.

Thus, referring to FIG. 5, the process of colour segmentation of step 58starts (at 80) by the user selecting a pixel (such as by clicking on it)or an area containing pixels (such as by clicking and dragging) of thecolour(s) the user wishes to segment. Each pixel of the colour selectedis identified by system 10 in a 3D colour referential map. This 3Dreferential map is, in this embodiment, RGB (Red, Green, Blue), but maytake any other suitable form, such as HLS(Hue, Lightness, saturation),HVS (Hue, Value, Saturation) or any other 3D colour scheme.

Then, from the selected colour pixel, colour segmenter 32 creates aseries of vectors (J), all starting from the initial pixel i. Vectors(J) represent all the directions in 3D space that could start from pixeli (though, for simplicity, only 27 directions are considered in thisdescription). Colour segmenter 32 then creates vectors representing allthe possible colours that could originate from pixel i. However, ascolour is a discreet event, a colour missing in a few pixels may notmean that this colour has not being selected by the user; thus, a notionof colour acuity (CA) is needed to capture the level of discreetness theuser may wish in the colour selection. The CA allows a more subtlesegmentation of colours in a given direction. However, the CA does notexceed the minimum perceptible colour difference (MPCD): this is thecolour difference between pixel i and the furthest away pixel (incolour) beyond which the user can clearly perceive that it has adifferent colour from that of pixel i. Both the CA and MPCD areadjustable and controllable by the user.

In each vector, only a distance from pixel i to the MPCD are analysed bycolour segmenter 32. Profiler 33 a of colour segmenter 32 creates acolour profile curve, and retrieves three or more colours and presentsthem to the user. If the user confirms the selection of thisautomatically selected cluster of colours, the selected colours can thenbe changed in the image according to the quantitative colouring (QC)method of this embodiment. If the user is not content with any of theautomatically selected colours, he or she may adjust the MPCD and CA, orincreasing the colour spectrum, in order to refine the detected colours.The user thus eventually finds the colours he or she wishes to change.

FIG. 6 includes schematic views of: (a) an example of colour pixel,represented in space as a voxel, representative of the colour to besegmented, (b) the same voxel with 19 of its 27 neighbours in 3D space,(c) the same pixel or voxel with all of its 27 neighbours, and (d) theposition of that pixel or voxel in a 3D colour referential.

The maximum length of vector (J) is determined by the unit in the coloursystem. In a 255*255*255 colour system, such as RGB, the maximumdiagonal is 441, so the maximum length of (J) is 441. Colour segmenter32 subdivides vector (J) into MPCD units, and each MPCD unit is thensubdivided into CA units. The default value of MPCD is 20 and of CA is5. However, these values are adjustable via user interface 16 a,b. Theprofile is only analysed in a length equal MPCD. If a pixel existswithin the image, its value is set to 1 in the vector, and if the pixelcolour does not exist in the image, it is set to 0. Values are thenaveraged over a length of CA and the obtained value is later used as yvalue on the colour profile curve. The portion of vector between pixel iand a distance corresponding to the MPCD is subdivided into nconsecutive points, with n being the number of CA portions within theMPCD. These n points form the x-axis of the colour profile curve whichis created, as shown in FIG. 7 which illustrates the creation of thevector of colours and the colour profile curve.

The colour profile curve starts at pixel i, selected by the user.Referring to FIGS. 8 to 10, the curve is analyzed by an analyser 33 b ofcolour segmenter 32 by, initially, detecting a point (s₁) correspondingto the smallest distance between pixel i of coordinates (0,0) and thecolour profile curve. Point (s₁) corresponds to the point where theselected colour along the vector has faded markedly. Then (m) isidentified as the point with the maximum y value in the portion of thecurve between pixel i and (s₁). From (m), this allows identification of(p) which has the same y value as (m) and an x value of (s₁). From (p),point (n) is identified as the smallest distance between (p) and thecolour profile curve. Point (n) corresponds to the point where theselected colour starts fading markedly. Finally, point (k) is identifiedas the inflexion point in the portion of the curve between (n) and (s₁).Point (k) is the point where the selected colour is fading at thehighest rate [see WO 2011/029153].

These points identify a cluster or range of colours that visuallycorrespond to the selected colour. Those of colour 1 correspond visuallyto the cluster of colours located between i and (n). Those of colour 2correspond to the cluster between pixel i and (k). Those of colour 3correspond to the cluster between pixel i and (s) (see FIG. 10).

It should be noted that this delineation of three colours cluster isindicative only. In principle any number of colours may be defined, suchas a fourth colour between (n) and (k). Furthermore, as shown in FIG.10, it may occur in some circumstances that the user sees that theidentified colours do not fully capture the range of colours he or shewishes to select and change. This will occur if colour the user wishedto select in fact encompasses a cluster of colours extending beyondpoint (s₁). The user will then press on ‘increase colour spectrum’. Thiswill trigger a re-analysis of the colour profile curve but this timestarting from point (R₁) which has the same x value as (s₁) but a yvalue of 0 and identify (s₂) a new colour 3 with a corresponding tocluster of colours between i and by (s₂) will be displayed and/or theimage change accordingly. If the user is not satisfied, he or she canagain trigger an ‘increase colour spectrum’, and a similar analysis ofthe curve is conducted but this time starting from s₂. It should benoted that the triggering ‘increase colour spectrum’ cannot be requestedindefinitely. The minimum distance from a point to a curve will retrievethe same point when the curve becomes horizontal relative to the x-axis,and/or the curve has been analysed along the full MPCD distance. Whenthis arises then the processor alerts the user that all colours withinthe profile that could be associated with the selected colours have beenidentified.

In each case, the resulting segmented colours are—at step 60—displayedto display 16 a by segmented colour displayer 34, thus informing theuser how the colours in the original image will be segmented: the colouror colours having a substantially identical appearance as the initiallyselected colour are displayed for user approval.

At step 62, the user may input his or her approval of the segmentationor, if desired, modify the segmentation using segmented colour modifier36.

At step 64, intensity determiner 39 of RIV determiner 38 determines aminimum intensity I_(MIN) and a maximum intensity I_(MAX) within theimage (or part thereof) to which the colours are to be assigned, and RIVdeterminer 38 orders all the intensity values within the image fromminimum intensity to maximum intensity, and normalizes these intensityvalues according to:

${N(i)}\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right)$

where N(i) is the normalized intensity, I(i) is the intensity of pixeli, and I_(MAX) and I_(MIN) are respectively the maximum and minimumintensity values within the image (or part thereof) to which the coloursare to be assigned (see FIG. 11). From the normalized intensity values,relative intensity values (RIV (i)) are then calculated, where RIV (i)=f(i)). The function f is of any desired and suitable form, such as alinear function, a polynomial function, an exponential function, alogarithmic function, or a Gaussian function. The function f is selectedsuch that its behaviour in the range N(i)=0 to 1 is predictable.Function f modifies the normalized intensity values N(i) in apredictable manner; it may for example magnify or shrink differences innormalized intensity values to highlight or reduce colour differencesbetween adjacent pixels, in order to make details more or less visiblelocally.

Relative intensity values and ordered colours are then associated asshown FIG. 12, which illustrates the operation of colour assignor 40. Anew function g is selected, which can also any desired and suitableform, such as a linear function, a polynomial function, an exponentialfunction, a logarithmic function, or a Gaussian function. The actualcolour to be assigned to each pixel is then determined by colourassignor 40 according to:

${{C(i)} = {{g\left( \frac{{{RIV}(i)} - {RIV}_{n}}{{RIV}_{n + 1} - {RIV}_{n}} \right)}\left( {C_{n + 1} - C_{n}} \right)}},$

where C(i) is the colour of pixel i, RIV(i) is the calculated value ofRIV for pixel i, RIV_(n) is the RIV of colour n and RIV_(n+1) is the RIVof colour n+1. C_(n) and C_(n+1) are the colours n and n+1 respectively.Function g, as in this example, may be set to

${{g\left( \frac{{{RIV}(i)} - {RIV}_{n}}{{RIV}_{n + 1} - {RIV}_{n}} \right)} = \left( \frac{{{RIV}(i)} - {RIV}_{n}}{{RIV}_{n + 1} - {RIV}_{n}} \right)},$

if the user does not desire to further manipulate the assignment ofcolours.

As stated above, allowing the user to select or modify function fprovides a mean for changing the relative importance of selected coloursto highlight or dampen details. In this embodiment an example of howthis works is shown in FIG. 13, which illustrates the modulationfunction f used to enhance or de-enhance some features in the image. Thefunction f selected is an exponential function, such as f=RIV(i)^(m).Changing the value of the exponent adjusts the relative dominance of thecolour first selected (i.e., low n) versus the colours selected last(high n), thereby highlight or toning specific details.

In this example:

-   -   When the exponent is m=1, all colours have the same importance.    -   As the exponent m increases above 1, the more colours first        selected dominate the image. That is, features with colours        selected first are more highlighted in the image.    -   The opposite effect occurs when the exponent m decreases and        becomes less than 1. The closer m is to 0, the more dominant        become features with high values of n (especially the last        colour selected).

Thus, the present invention provides a method and system forautomatically (or manually if desired) highlighting specific details inany image using gradient of colours which reflects, and magnifies, therelative differences in intensity values between pixels or voxels in aselected parts of the image. This thereby allows the creation of aclearer visualization of details in specific areas of the image, or inobjects within the image, or in entire image.

Modifications within the scope of the invention may be readily effectedby those skilled in the art. It is to be understood, therefore, thatthis invention is not limited to the particular embodiments described byway of example hereinabove.

In the claims that follow and in the preceding description of theinvention, except where the context requires otherwise owing to expresslanguage or necessary implication, the word “comprise” or variationssuch as “comprises” or “comprising” is used in an inclusive sense, thatis, to specify the presence of the stated features but not to precludethe presence or addition of further features in various embodiments ofthe invention.

Further, any reference herein to prior art is not intended to imply thatsuch prior art forms or formed a part of the common general knowledge inany country.

1. A computer-implemented method for segmenting a cluster of colours within an image, the method comprising: identifying or selecting at least one colour within the image; creating a colour profile curve from a reference point (x_(i), 0) corresponding to the at least one colour to all colours in a selected colour scheme; analysing the colour profile curve by detecting a closest point (s₁) on the colour profile curve to the reference point (x_(i), 0); locating a point of inflexion on the colour profile curve between the reference point (x_(i), 0) and the closest point (s₁); and segmenting a portion of the colour profile curve between the reference point (x_(i), 0) and the point of inflexion, the segmented portion of the colour profile curve constituting a cluster of colours corresponding to the at least one colour.
 2. A method as claimed in claim 1, wherein a length of the colour profile curve is a minimum perceptible colour difference and the method includes an optional step of adjusting the minimum perceptible colour difference.
 3. A method as claimed in claim 2, including subdividing a length of the colour profile curve between the reference point (x_(i), 0) and a point corresponding to the minimum perceptible colour difference into a set of colours.
 4. A method as claimed in claim 3, wherein the length of the colour profile curve between the reference point (x_(i), 0) and a point corresponding to the minimum perceptible colour difference is equal to the minimum perceptible colour difference for a colour.
 5. A method as claimed in claim 1, further comprising automatically segmenting another cluster of colours by automatically analysing another portion of the colour profile curve.
 6. A method as claimed in claim 3, including automatically determining when all colours within the desired cluster of colours have been identified.
 8. A method as claimed in claim 1, further comprising assigning different colours to the segmented colours.
 9. A method as claimed in claim 8, wherein assigning colours to the image or part thereof, comprises: selecting a sequence of colours for assignment to the image or part thereof; determining a minimum intensity I_(MIN) within the image or part thereof; determining a maximum intensity I_(MAX) within the image or part thereof; and determining relative intensity values RIV(i) for each pixel or voxel i according to: ${{RIV}(i)} = {f\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right)}$ where I(i) is an intensity of pixel or voxel i, and f is a preselected function; and assigning colours to at least some pixels in the image or part thereof based on the relative intensity values and an order of each of the colours in the sequence.
 10. A method as claimed in claim 9, comprising: (i) selecting colours or shades in the original image and applying the method only to pixels or voxels of the colours or shades thus selected, and/or (ii) selecting automatically the image or a part thereof based on one or more criteria.
 11. A method as claimed in claim 9, wherein ${f\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right)} = {\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right).}$
 12. A method as claimed in claim 9, comprising generating a new image by colouring the image according to the sequence of colours.
 13. A system for segmenting cluster of colours within an image, the system comprising: a colour selector for identifying or selecting at least one colour within the image; a profiler for creating a colour profile curve from a reference point (x_(i), 0) corresponding to the at least one colour to all colours in a selected colour scheme; and an analyser for analysing the colour profile curve by detecting a closest point (s₁) on the colour profile curve to the reference point (x_(i), 0), locating a point of inflexion on the colour profile curve between the reference point (x_(i), 0) and the closest point (s₁), and segmenting a portion of the colour profile curve between the reference point (x_(i), 0) and the point of inflexion, the segmented portion of the colour profile curve constituting a cluster of colours corresponding to the at least one colour.
 14. A system as claimed in claim 13, comprising an output for outputting the colour or colours having the substantially identical appearance as the initially selected colour.
 15. A system as claimed in claim 13, wherein the colour scheme is a RBG (Red, Blue, Green) colour scheme, an HLS (Hue, Lightness, saturation) colour scheme, or an HVS (Hue, Value, Saturation) colour scheme.
 16. A system as claimed in claim 13, wherein a length of the colour profile curve is a minimum perceptible colour difference.
 17. A system as claimed in claim 16, the system enabling adjusting the minimum perceptible colour difference.
 18. A system as claimed in claim 16, wherein the analyser subdivides a length of the colour profile curve between the reference point (x_(i), 0) and a point corresponding to the minimum perceptible colour difference into a set of colours.
 19. A system as claimed in claim 18, wherein the length of the colour profile curve between the reference point (x_(i), 0) and a point corresponding to the minimum perceptible colour difference is equal to the minimum perceptible colour difference for a colour.
 20. A system as claimed in claim 13, further comprising automatically segmenting another cluster of colours by automatically analysing another portion of the colour profile curve.
 21. A system as claimed in claim 18, including automatically determining when all colours within the desired cluster of colours have been identified.
 22. A system as claimed in claim 13, further comprising assigning different colours to the segmented colours.
 23. A system as claimed in claim 13, further comprising: a colour selector for selecting a sequence of colours for assignment to the image or part thereof; an intensity determiner for determining a minimum intensity I_(MIN) within the image or part thereof, and for determining a maximum intensity I_(MAX) within the image or part thereof; a relative intensity value determiner for determining a relative intensity value RIV(i) for each pixel or voxel i according to: ${{RIV}(i)} = {f\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right)}$ where I(i) is an intensity of pixel or voxel i, and f is a preselected function; and a colour assignor for assigning colours to at least some pixels in the image or part thereof based on the relative intensity values and an order of each of the colours in the sequence.
 24. A system as claimed in claim 23, comprising an image outputter for generating a new image by colouring the original image according to the sequence of colours.
 25. A system as claimed in claim 23, wherein ${f\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right)} = {\left( \frac{{I(i)} - I_{MIN}}{I_{MAX} - I_{MIN}} \right).}$
 26. A system as claimed in claim 23, configured to select automatically the image or a part thereof based on one or more criteria.
 27. A system as claimed in claim 23, comprising an output for outputting the colour or colours having the substantially identical appearance as the initially selected colour. 